Bonding pads are interfaces to connect the electric components inside a semiconductor device to exterior devices. Bonding pads electrically connect to components inside the semiconductor device by filling vias etched into the semiconductor device. Bonding pads electrically connect to exterior devices by accepting conductive connectors such as solder balls or wires which are electrically connected to exterior devices.
In order for a bonding pad to be effective, the bonding pad must completely fill the via, otherwise electrical connection to components inside the semiconductor device is not properly established. The bonding pad must also be strong enough to withstand the impact of wire bonding or pressing of another semiconductor device against a solder ball.
Conventional techniques use aluminum as a material for the bonding pad. The aluminum bonding pad is deposited in one process step using physical vapor deposition. Obtaining acceptable strength and via filling is difficult because the deposition process is a single step. High temperature physical vapor deposition provides better via filling but has poor strength which can cause the bonding pad to fracture upon impact when connecting to exterior devices. In the case of wire bonding, if the bonding pad is not strong enough the wire may pull out of the bonding pad during the wire bonding process. Low temperature physical vapor deposition provides high enough strength to withstand the impact of connecting to exterior devices but provides poor via filling.